In some installations, such as French doors, it is desirable to use a pair of locksets, typically handlesets, with one mounted on each door. At the same time, it is preferable to have one of the locksets operate the latching mechanism, with the other lockset being incapable of functioning. In the past, manufacturers have made add-on conversion kits that render a functional lockset inoperative by blocking the movement of the latch actuating mechanism. Unfortunately, such dummy locksets necessarily include many unused parts that add to the cost of the lockset without adding any value to the product.
In the case of a handleset, which uses a thumbpiece to actuate the latch, mere removal of the latch actuating mechanism would leave the thumbpiece unsupported. As a result, the thumbpiece would drop down to rest on the handle, giving the appearance of a broken handleset, which would be unacceptable to consumers.